re: What pushes it to orbit
It is an airship-derived spacecraft. It flies horizontally like an airship, powered by a low thrust reaction drive such as an electric rocket engine. It will employ bouyancy and aerodynamic lift at the beginning of its flight rather than the high vertical thrust of conventional missile-derived launch vehicles. Taking advantage of the rapid variation in atmospheric properties at mesospheric and thermospheric altitudes, it will be able to maintain sufficient horizontal velocity to provide aerodynamic lift all the way up to orbit.
I haven't read much detail on it, but I have read enough to feel confident that it will not glide into space ala Stevie Smyth who has spammed this board from time to time. :)